Although nanotechnology has experienced dramatic development in the area of electronics and devices, some key challenges have to be overcome in order to reach the stage of nanoelectronics manufacturing and commercialization. To date, one major challenge in nanoelectronics and device research is the effective joining of nanoelements (such as nanowires or carbon nanotubes) with low contact resistance to obtain reliable electrical and thermal interconnection. Tin/lead solders have long been used as interconnect materials in the electronic and microelectronic industries. Lead-free solders are being developed due to environmental and safety concerns with lead. Such lead-free solders preferably have a low melting point, should readily wet bond pads to provide reliable bonding between components, and should be available at low cost. However, many lead-free solders are not eutectic and normally require higher processing temperatures. Therefore, nanoscale lead-free solders have been suggested due to the unique properties of materials at the nanoscale, including large surface area per unit volume, large surface energy, and low melting point. The melting temperature depression can reduce the reflow processing temperature and reduce thermal stresses during processing. Further, the finer microstructure can provide increased strength of the solder alloy and higher service temperatures. Finally, nanosolders allow interconnect miniaturization, enabling very small pitch applications and increased fine pitch interconnect reliability.
However, a need remains to understand the synthesis-structure-property relationships in nanosolders for joining/bonding applications to enable further miniaturization of nanoelectronic devices with high quality and reliability. Such lead-free nanosolder materials and nano-soldering techniques could play a key role in the electronics industry, as well as in various areas of advanced materials joining, including medical devices, nanoelectromechanical systems (NEMS), sensors, aerospace and defense industries.